Scientist discovered blackpoll warbler birds migrate 1,700 miles across the ocean, flying from the forests of northeastern United States and eastern Canada to the Caribbean as part of their winter migration every year.

Its migration to the Caribbean over the ocean was already suspected by scientists but this is the first time they managed to prove it.

In a bid to confirm the bird s annual migration route and distance it covers, the researchers outfitted the bird with even tinier tracking devices, dubbed backpacks.

As part of the study, the researchers used tiny geo-locators -- each weighing only 0.5 gram -- to track blackpolls on their annual flight south to the Caribbean, and on their way north to Canada and the U.S. in the spring. The devices, which were fitted on the backs of the birds, were so small that they were not able to transmit the data remotely and researchers had to wait until the birds returned.

We waited for them to return in the spring and then searched the forest to find the blackpolls with geo-locators, William DeLuca of the University of Massachusetts and the study s co-author, said in the statement. When we accessed the locators, we saw the blackpolls journey was indeed directly over the Atlantic. The distances travelled ranged from 2,270 to 2,770 km.

This is the first study to provide direct evidence of the birds migration route we found they flew directly over the Atlantic Ocean to reach their wintering grounds in South America, Ryan Norris, a professor at the University of Guelph in Ontario, Canada, and the study s co-author, said in a statement.

It is such a spectacular, astounding feat that this half-an-ounce bird can make what is obviously a perilous, highly risky journey over the open ocean, said Chris Rimmer of the Vermont Center for Ecostudies, one of the authors.

The warblers, known to bulk up by eating insects near their coastal departure points before heading south, are common in parts of North America, but their numbers have been declining. Now maybe that will help us focus attention on what could be driving these declines, Rimmer said.

The findings of the study were published on Tuesday in the journal Biology Letters.